I recently purchased a 2005 Kawasaki Vulcan 500 and was told to always use 91 but I am hearing a kind of clanking when I get heavy on the throttle to get going after checking my owners manual I believe it said either could be used but with everything on it being stock do I need to empty out the fuel and stick with 85 or 87? and hope that me putting the higher octane fuel didn’t mess up the bike